With the evolution of more complex utility infrastructures requiring enhancement, replacement, and expansion in many areas of human use or occupation, and in particular high-density areas such as cities and suburbs, the ability to accurately map the location of buried utilities such as conduits, wires and pipelines of various sizes and types becomes more pressing, as does the need to document actual as-built underground utility installations before they are covered so that they can be precisely located at a later date.
Worker safety and economic concerns also require the location and identification of existing underground utilities such as underground power lines, gas lines, phone lines, fiber optic cable conduits, cable television (CATV) cables, sprinkler control wiring, water pipes, sewer pipes and the like, which are collectively and individually referred to herein as “buried objects” or “buried utilities.”
The unintended destruction of power and data cables can seriously disrupt the comfort and convenience of residents, and can cause huge financial costs to businesses. Breakage of gas lines can cause likewise cause economic harm as well as serious personal injury or death. Therefore human-portable buried object locators (also denoted herein for brevity as “utility locators” or simply “locators”) have been developed to locate buried utilities by sensing electromagnetic signals, typically magnetic fields, emitted by the utilities due to currents flowing in them.
Buried objects are frequently located by utility employees or other uses by moving a utility locator over the ground or other areas where a utility is suspected of being present. The locator is moved over the ground or other surface by an operator, and receives and processes electromagnetic signals emitted from the utilities to determine, for example, information about the buried utilities' position underground and relative to the ground surface (e.g., in relative terms with respect to the user and/or in geographic latitude/longitude or other coordinate systems), depth below ground, utility type, multiple utility configurations (when more than one utility is present) and the like. These operations are commonly known in the art as “line tracing” or “locates.”
If the buried utilities are conductors that carry their own electrical signal, such as electrical power lines, they can be traced by detecting the emitted signals at their corresponding frequency or frequencies, such as 50 or 60 Hz or harmonics thereof for underground power lines, also known as “passive locating.” Signals with a known frequency may also be applied to pipes and cables via a device known as a “locate transmitter” or “transmitter” for short, which may be directly, inductively, or capacitively coupled to the utility to enhance the ease and accuracy of the line tracing operation, also known as “active locating.” In some operations, a device known as a sonde, which includes a magnetic dipole antenna and current signal generation module, is inserted into a pipe, conduit or other cavity and generates a magnetic field signal that can be detected by a locator. During these operations it is desirable to track the position and location of the locator or other device throughout its movement, either in relative coordinates, absolute coordinates or both.
Portable utility locators typically carry one or more antennas that are used to detect the electromagnetic signals emitted by buried utilities and by sondes that have been inserted into pipes or other cavities. In addition, some underground utility installations use devices known as marker balls, which are commonly in the shape of a sphere and function by receiving electromagnetic energy emitted from a standalone dedicated transmitter device and generate return signals indicating their presence. These marker balls are placed in the ground to provide an additional way to identify hidden objects by receiving a dedicated signal from them, which is typically initiated by a separate pulsed transmission to the device to provide RF energy for powering the marker ball. In existing systems, the transmit and receive frequencies in marker ball systems are typically the same for the pulsed excitation or “ping” and the return signal from the marker ball.
In addition, other similar electromagnetic identification devices are used for other applications, such as radio frequency identification (RFID) tags used to track inventory or merchandise and the like. These marker ball and RFID devices all require dedicated transmitters to send electromagnetic energy to the ball or tags to energize them so they can respond. In these systems, the transmit signals are typically sent in pulses because the return signal is on the same frequency and the transmit signal would overload the receiver input of any device attempting to sense the much lower signal levels from the marker ball or RFID device.
Because of various problems related to signal transmission and reception in single devices as developed in the art, no systems have been developed to integrate marker transmitters functionality with associated marker devices and corresponding locators to provide an integrated solution that allows for simultaneous detection of marker devices while excitation signals are being sent (e.g., excitation signals in these devices are sent in a pulsed or on-off fashion so that the excitation transmissions are turned off during time intervals when signals from the marker balls or buried utilities are being received). Moreover, existing marker ball devices typically trade off size for power, range, and/or data capability, and tend to be relatively expensive.
Accordingly, there is a need in the art to address the above-described as well as other problems related to marker devices and associated locator systems.